JP2008089408A - Lighting system, and surface state inspection apparatus having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting means capable of accurately detecting a defect on a cylindrical surface of a cylindrical object, and a lighting system using the lighting means. <P>SOLUTION: In this lighting system, a plurality of lighting means for emitting parallel light are arranged around the shaft extended from the cylinder shaft of the cylindrical object, and the cylindrical surface is lit diagonally to the normal by the light emitted from the plurality of lighting means. The plurality of lighting means are arranged so that the perpendicular distance of the cylinder shaft is constat, and incident angles of the main light beams of light when the light is radiated to the cylindrical surface of the cylindrical object are equal mutually. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an illuminating device and a surface state inspection device having the same, and is suitable for, for example, inspecting a surface state such as a defect of a cylindrical surface and a uniformity of a rough surface (roughness) with high accuracy. .

  2. Description of the Related Art Conventionally, there is known a method for detecting the presence or absence of minute defects (scratches or adhesion of foreign matter) present on an object surface using light.

  In general, the object to be inspected is irradiated with uniform intensity light from the illumination means, and a photographed image of the reflected light distribution consisting of specular reflection light and diffuse reflection light from the surface is obtained. We inspect defects such as minute unevenness.

  At this time, the incident angle of the irradiation light on the surface to be inspected is set to approximately 45 ° or more, and the surface of the object to be inspected is irradiated at a low angle (large tilt angle) to inspect the presence or absence of defects on the surface. The method is known.

As a surface to be inspected, a device that inspects a cylindrical surface of a cylindrical object by irradiating light with a high degree of parallelism on the cylindrical surface of the cylindrical object obliquely and detecting diffuse reflection light generated from the cylindrical surface is known. . (See Patent Document 1).
Japanese Patent Laid-Open No. 2-115706

  8 and 9 are schematic views of the main part of an inspection apparatus that automatically inspects the surface of a cylindrical part disclosed in Patent Document 1. FIG.

  FIG. 8 is a plan view seen from the direction perpendicular to the central axis 1b of the cylindrical object 1, and FIG. 9 is a plan view seen from the central axis direction of the cylindrical object. Reference numeral 1 denotes a cylindrical object, 3 denotes a parallel light beam having a high degree of parallelism, and 7 denotes a camera. Reference numerals 30, 31, 32, and 33 denote rays in the parallel light flux, and incident angles with respect to the tangent of the cylindrical shape 1 are θi0, θi1, θi2, and θi3, respectively. Reference numerals 30 ′, 31 ′, 32 ′, and 33 ′ indicate specularly reflected light components of the light beams 30, 31, 32, and 33, respectively.

  When viewed from the direction of FIG. 8, the light 3 is incident on the surface (cylindrical surface) 1 a of the cylindrical object 1 at the same incident angle. For this reason, the reflection direction of regular reflection light is the same. That is, the illuminance unevenness does not occur in the direction of the axis 1b in the image photographed by the camera 7.

  On the other hand, when viewed from the direction shown in FIG. 9, it can be seen that the surface 1a of the cylindrical object 1 has a curvature, and the incident angle with respect to the cylindrical surface 1a varies depending on the incident position even when the parallel light 3 is incident. Therefore, the regular reflection light angle also changes according to the incident angle.

  FIG. 10 shows a general reflected light distribution when light is incident on the rough surface. The distribution (reflected light intensity distribution) is such that the amount of light decreases as the specular reflection direction reaches the peak. That is, the amount of light in the direction in which the camera 7 is located is large for the light rays 30 and 31 that are close to the regular reflection direction, and is small for the light rays 32 and 33 that are far from the regular reflection direction.

  That is, since the amount of light on the image decreases as the distance from the central axis 1b increases, unevenness in the amount of light occurs in the circumferential direction of the cylindrical object 1.

  Therefore, when the cylindrical object 1 is photographed by the camera 7, the captured image 1P has a bright central portion 1bb and a dark peripheral portion 1aa as shown in FIG. Although a certain amount of light amount unevenness can be corrected by performing shading correction, there is a risk that noise may be increased, and therefore the circumferential region that can be used for defect detection is limited.

  When photographing the entire surface 1a of the cylindrical object 1, it is necessary to photograph while rotating the cylindrical object 1 or the camera 7, and the number of times of photographing increases when the photographing effective area is small. Since defect inspection of the surface to be inspected at the production site requires high speed, fewer shots are preferred.

  In the invention of Patent Document 1, an effective means for solving such unevenness in the amount of light is not specified.

  In order to improve the accuracy of automatic inspection of defects on the circumferential surface, the illuminance uniformity and directivity on the cylindrical surface of the irradiated light are important. If the illuminance of the irradiation light is not uniform, unevenness in illuminance occurs in the captured image of the cylindrical surface, causing false detection.

  In addition, when the directivity of the irradiation light is low, the detection sensitivity greatly changes due to the variation of the incident angle in the defect having a high incident angle dependency of the reflected light distribution.

  An object of this invention is to provide the illumination means which can detect the defect on the cylindrical surface of a cylindrical object with high precision, and the surface state inspection apparatus using the illumination means.

The illumination device of the present invention has a plurality of illumination means for emitting parallel light around an axis obtained by extending the cylindrical axis of a cylindrical object,
An illumination device that illuminates the cylindrical surface with light from the plurality of illumination means obliquely with respect to the normal line,
The plurality of illumination means includes:
The distances in the vertical direction of the cylindrical axes are equal, and the incident angles of the principal rays of light when irradiating the cylindrical surface of the cylindrical object are equal to each other.

Further, the surface condition inspection apparatus of the present invention has a plurality of illumination means for emitting parallel light around an axis obtained by extending the cylindrical axis of a cylindrical object,
An illuminating device that illuminates the cylindrical surface with light from the plurality of illumination means obliquely with respect to the normal line;
An imaging device for photographing the cylindrical surface;
From the image information obtained by the imaging device, a surface state inspection device having processing means for inspecting the surface state on the cylindrical surface,
The plurality of illumination means includes:
The distances in the vertical direction of the cylindrical axes are equal, and the incident angles of the principal rays of light when irradiating the cylindrical surface of the cylindrical object are equal to each other.

Further, the surface condition inspection method of the present invention is around the axis obtained by extending the cylindrical axis of the cylindrical object,
An illuminating device in which a plurality of proving means are arranged so that the vertical distances of the cylindrical axes are equal, and the incident angles of chief rays of light when illuminating parallel light onto the cylindrical surface of the cylindrical object are equal to each other An irradiation step of illuminating the cylindrical axis with light from the oblique direction with respect to the normal line;
A photographing step of photographing the cylindrical surface with an imaging device;
Processing the image information obtained by the imaging device with a processing means, and inspecting defects on the cylindrical surface;
It is characterized by having.

  According to the present invention, a defect on a cylindrical surface of a cylindrical object can be detected with high accuracy.

  Examples according to the present invention will be described below.

  FIG. 1 is a plan view seen from a direction perpendicular to the central axis of the cylindrical object according to the first embodiment, and FIG. 2 is a plan view seen from the central axis direction of the cylindrical object according to the first embodiment. 1 and 2, reference numeral 1 denotes a cylindrical object. Reference numeral 2 denotes an afocal optical system unit (parallel light flux generating means) as an illuminating means. Reference numeral 3 denotes a parallel light beam emitted from the afocal optical system unit 2. Reference numeral 4 denotes a principal ray of the parallel light beam 3, and 7 denotes a camera (imaging device).

  Reference numeral 8 denotes processing means. All afocal optical system units 2 use the axis (cylindrical axis) 1b of the cylindrical object 1 so that the principal ray 4 of the emitted parallel light beam enters the cylindrical surface 1a of the cylindrical object 1 at the same angle θi. Located around the extended shaft.

  Further, as shown in FIG. 2, all afocal optical system units 2 are arranged at equal angular intervals with respect to the axis 1b of the cylindrical object 1 with the same distance from the axis 1b. The camera 7 is arranged so that the optical axis 7 b of the optical system 7 a constituting the camera 7 is perpendicular to the axis 1 b of the cylindrical object 1. In order to photograph the entire surface of the cylindrical object 1 (the entire cylindrical surface) with a single camera 7, the cylindrical object 1 may be imaged while rotating about the axis 1b. The motor for rotating the cylindrical object 1 is omitted in the drawing.

  Alternatively, a plurality of cameras may be arranged at equiangular intervals with the central axis 1b of the cylindrical object 1 as the rotation axis, and the entire surface of the cylindrical surface 1a may be photographed.

  The processing means 8 uses the image information obtained by the camera 7 to inspect the surface condition such as defects on the cylindrical surface 1a.

  The plurality of afocal optical units 2 are around the axis obtained by extending the cylindrical axis 1b of the cylindrical object 1 and have the same distance in the vertical direction of the cylindrical axis 1b, and light is incident on the cylindrical surface 1a of the cylindrical object 1. Are arranged so that the incident angles of the chief rays of the light when irradiating are equal to each other.

  In this embodiment, a plurality of afocal optical system units 2 emit parallel light beams so as to face the center of the cylindrical object 1. For this reason, the illuminance distribution on the cylindrical surface 1a of the cylindrical object 1 is uniform. Next, the reason will be described.

  In the present embodiment, eight afocal optical units (hereinafter also simply referred to as “units”) 2 are provided.

  The arrangement angle interval of the unit 2 with respect to the axis 1b of the cylindrical object 1 is 45 °.

  The angles θc formed by the optical axis 2a of each unit 2 and the camera 7 are four types of 0 °, 45 °, 90 °, and 135 °, respectively, considering symmetry.

  Plan views of the cylindrical object 1 viewed from the direction of the central axis 1b when the angles formed by the camera 7 and the unit 2 are 0 °, 45 °, 90 °, and 135 ° are shown in FIGS. 12, 13, 14, and 15, respectively. Show.

  12 to 15 also show the light amount distribution of an image taken by the camera 7 when the cylindrical surface 1a of the cylindrical object 1 has the reflected light distribution of FIG.

  It can be seen that when the angle θc formed by the camera 7 and the unit 2 increases, the peak position of the light amount on the image shifts from the center to the left and right due to the change in the regular reflection direction.

  Therefore, as shown in FIGS. 16A to 16E, when the light sources of all the units 2 are turned on and the added light quantity is photographed by the camera 7, the light quantity distribution is almost flat as shown in FIG. become.

  In this embodiment, the number of units 2 is eight, but the number of units 2 is not limited to eight. Since the uniformity of illuminance on the cylindrical surface 1a increases as the interval between the units 2 is reduced and the density is increased, the number of units 2 is preferably larger.

  Next, the configuration of the afocal optical system unit 2 will be described with reference to FIG. In FIG. 3, 21 is a light source, 22 is a collimating lens (collimating optical system), 23 is an object side lens (first optical system), 24 is an aperture, and 25 is an image side lens (second optical system).

  As the light source 21, an illumination means such as an incandescent bulb, a halogen lamp, an Xe tube, or a light emitting diode can be used. Moreover, although it is possible to use a constantly lit illumination or a stroboscopic light source, it is preferable to use a stroboscopic light source when photographing a cylindrical object a plurality of times while rotating it at high speed.

  The light source 21 is disposed on the optical axis 2a at a position separated from the collimating lens 22 by the focal length F1 of the collimating lens 22. The distance from the lens is a distance from the principal point position. The same applies hereinafter. Therefore, the spherical wave emitted from the light source 21 is converted into a plane wave, that is, parallel light by the collimator lens 22.

  Further, the object side lens 23 and the image side lens 25 are arranged apart from each other on the optical axis by a distance F2 + F3 obtained by adding the focal length F2 of the object side lens 22 and the focal length F3 of the image side lens.

  An optical system having such a lens 23 and lens 25 is called an afocal optical system. When light having a beam diameter D1 is incident on the object side lens 23, the light is emitted with a beam diameter D2 that satisfies the following relational expression (1).

D2 = D1 × F3 / F2 (1)
That is, by appropriately selecting the focal length F2 of the object side lens 23 and the focal length F3 of the image side lens 25, parallel light having an arbitrary beam diameter can be created.

  In order to ensure the illuminance uniformity in the axis 1b direction of the cylindrical object 1, it is necessary to irradiate the entire surface 1a of the cylindrical object 1 with a beam as shown in FIG. That is, the outgoing beam diameter D2 needs to satisfy the following inequality (2).

D2> L × cos θi (2)
Here, L is the length of the cylindrical object 1 in the axis 1b direction, and the angle θi is the incident angle of parallel light (chief ray). It is preferable to arrange the afocal optical system units 2 at high density in order to increase the uniformity of illuminance. However, the relationship of the expression (2) is restricted by the length L of the cylindrical object 1 and the incident angle θi. That is, the density that can be arranged is inversely proportional to the length L of the cylindrical object 1 and proportional to the incident angle θi.

  By arranging the aperture 24 at the position of the point P where the focal point of the object side lens 23 coincides with the focal point of the image side lens 25, the directivity of the parallel light can be controlled. When the aperture diameter of the aperture 24 is reduced, the directivity of parallel light increases, and when the aperture diameter of the aperture 24 is increased, the directivity of parallel light decreases. Therefore, the detection sensitivity of the defect on the cylindrical surface 1a and the light use efficiency can be selected by changing the aperture diameter of the aperture 24 in accordance with the incident angle dependency on the cylindrical object 1.

  FIG. 18 is a flowchart of the surface condition inspection method of the present invention. In FIG. 18, S1 is an irradiation process. In the irradiation step S1, the cylindrical surface 1a is illuminated obliquely with respect to the normal line with light from an illuminating device in which a plurality of illuminating units 2 that emit parallel light are arranged.

  S2 is a photographing process. In the photographing step S2, the cylindrical surface 1a is photographed by the imaging device 7.

  S3 is an inspection process. In the inspection step S3, the image information obtained by the imaging device 7 is processed by the processing means 8 to inspect defects on the cylindrical surface 1a.

  According to the present embodiment, as described above, the plurality of parallel light flux generating means 2 are arranged with respect to the axis 1b of the cylindrical object 1, so that the surface (cylindrical surface) 1a of the cylindrical object 1 has high directivity, and Uniform illumination is possible. Thereby, the defect on the cylindrical surface 1a can be detected with high sensitivity and high speed.

  FIG. 5 is a plan view seen from the direction perpendicular to the central axis 1b of the cylindrical object 1 of the second embodiment, and FIG. 6 is a plan view seen from the direction of the central axis 1b of the cylindrical object 1 of the second embodiment. Reference numeral 5 denotes a minute lens (first optical system), and reference numeral 6 denotes a shared lens (shared optical system) shared by each light source 21 and the minute lens 5. In the second embodiment, an off-axis optical system 20 is configured by a plurality of microlenses 5 and a shared lens 6.

  The off-axis optical system 20 of the present embodiment will be described with reference to FIGS. FIG. 3 shows a normal afocal optical system 2, and FIG. 7 shows an off-axis optical system 20. As shown in FIG. 7, even in the off-axis optical system 20, the minute lens 5 and the shared lens 6 are arranged apart from each other by the sum of the focal length F <b> 4 of the minute lens 5 and the focal length F <b> 5 of the shared lens 6.

  However, the normal afocal optical system 2 shown in FIG. 3 is arranged so that the optical axis of the object side lens 23 and the optical axis of the image side lens 25 coincide. On the other hand, the off-axis optical system 20 is arranged so that the optical axis 5a of the minute lens 5 and the optical axis 6a of the shared lens 6 are shifted by a distance J as shown in FIG.

  In the afocal optical system, the traveling direction of the outgoing parallel light is parallel to the optical axis, but in the off-axis optical system, the optical axes of the two lenses 5 and 6 are shifted, so the traveling direction of the outgoing parallel light is the same as that of the shared lens 6. It is not parallel to the optical axis 6a, but is shifted by an angle θj.

  The angle deviation amount θj can be calculated by the following relational expression (3).

θj = tan ⁻¹ (J / F5) (3)
Here, J is the amount of deviation between the optical axis 5a of the minute lens 5 and the optical axis 6a of the shared lens 6, and F5 is the focal length of the shared lens 6. There is the following relationship (4) between the incident angle θi of light on the cylindrical surface 1a and the angle shift amount θj. For this reason, the incident angle θi of the light beam to the cylindrical surface 1a of the cylindrical object 1 can be arbitrarily set by appropriately determining the angle deviation amount θj.

θi = 90 ° −θj (4)
The principal ray 4 of the parallel light beam intersects at a point P3 on the optical axis 6a of the shared lens 6 and separated from the shared lens 6 by the focal length F5 of the shared lens 6. Therefore, the cylindrical object 1 is arranged so that the center in the longitudinal direction coincides with P3, and the beam diameter D4 when light is emitted from the shared lens 6 satisfies the following expressions (5) and (6). If the focal length of the lens is selected, the cylindrical object 1 can be uniformly illuminated in the direction of the axis 1b.

D4 = D3 × F5 / F4 (5)
D4> L × cos θi (6)
Even in the configuration using the multiplexed off-axis optical system 20 of the second embodiment, the camera 7 has uneven light quantity in the circumferential direction of the cylindrical surface 1a for the same reason as the configuration using the multiplexed afocal optical system of the first embodiment. Fewer images can be obtained.

  In the case of the first embodiment, the outgoing beam diameter D2 cannot be made larger than the diameter of the image side lens 25. On the other hand, in Example 2, if the magnification (F5 / F4) of the off-axis optical system 20 is larger than 1, the cylindrical surface 1a is irradiated with an output beam diameter D4 larger than the beam diameter D3 when the microlens 5 is incident. Can do.

  As a result, since each outgoing beam can be overlapped, the illuminance uniformity can be further improved.

  In the case of Example 1, it is necessary to tilt the afocal optical system unit 2 obliquely. On the other hand, in the case of Example 2, since the microlenses 5 are present in the same plane, the alignment operation is relatively easy.

  In both the first and second embodiments, the optical axis of the optical system 7a of the camera 7 is arranged so as to be perpendicular to the central axis 1b of the cylindrical object 1. However, as shown in FIG. You may incline and incline by arbitrary angle (theta) a with respect to 1b.

  When the tilt angle θa of the camera 7 is the same as the incident angle θi of the parallel light flux (that is, θa = θi), the specularly reflected light component is incident on the camera 7, so that a bright field image can be taken.

  On the other hand, when the tilt angle θa of the camera 7 is set to an angle different from the incident angle of the parallel light flux (that is, θa ≠ θi), the scattered light component is incident on the camera 7, and thus a dark field image can be taken.

  When the optical axis 7b of the optical system 7a of the camera 7 is arranged perpendicular to the central axis 1b of the cylindrical object 1, the cylindrical object 1 is distorted in the direction of the axis 1b in a special case where θa = 0 °. You can shoot without.

  On the other hand, when the camera 7 is arranged so that θa ≠ 0 °, geometric distortion generated in the image needs to be corrected. However, since the surface 1a of the cylindrical object 1 can be observed in two states of a bright field image and a dark field image from an oblique direction, a defect on the cylindrical surface 1a can be obtained by performing a specific calculation process between both images. The site can be emphasized.

The top view seen from the direction perpendicular | vertical to the central axis of the cylindrical object of Example 1 of this invention The top view seen from the central-axis direction of the cylindrical object of 1st Example 1 of this invention Plan view showing the afocal optical system unit of FIG. The top view which showed the relationship of the output beam diameter of parallel light, incident angle, and the length of a cylindrical object regarding the afocal optical unit of FIG. The top view seen from the direction perpendicular | vertical to the central axis of the cylindrical object of Example 2 of this invention The top view seen from the central-axis direction of the cylindrical object of Example 2 of this invention FIG. 5 is a plan view showing a partly off-axis optical system in FIG. Plan view of a conventional cylindrical object surface inspection device viewed from a direction perpendicular to the central axis of the cylindrical object Plan view of a conventional cylindrical object surface inspection device as seen from the central axis direction of the cylindrical object Illustration of general reflected light distribution Image of a cylindrical object taken with a conventional cylindrical object surface inspection device A plan view of the cylindrical object viewed from the central axis direction when θc = 0 ° in Example 1 and a light amount distribution of the photographed image A plan view of the cylindrical object viewed from the central axis direction when θc = 45 ° in Example 1 and the light amount distribution of the photographed image A plan view of the cylindrical object viewed from the central axis direction when θc = 90 ° in the first embodiment and the light amount distribution of the photographed image A plan view of the cylindrical object viewed from the central axis direction when θc = 135 ° in the first embodiment and the light amount distribution of the photographed image Light intensity distribution of a captured image when θc = 0 °, ± 45 °, ± 90 °, ± 135 ° in Embodiment 1 and a captured image obtained by adding all of them The top view when the camera is inclined obliquely with respect to the central axis of the cylindrical object in the present invention Flow chart of surface condition inspection method of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylindrical object 2 ... Afocal optical system unit 3 ... Parallel light beam 4 ... Main ray 5 of parallel light beam ... Micro lens 6 ... Shared lens 7 ... Camera 8 ..Processing means 20: off-axis optical system 21 ... light source 22 ... collimating lens 23 ... object side lens 24 ... aperture 25 ... image side lens 30 ... in parallel light flux Ray 30 '... Specularly reflected light 31 of ray 30 ... Ray 31' in parallel light flux ... Specularly reflected light 32 of light beam 31 ... Light ray 32 'in parallel light flux ... Positive light 32 Reflected light 33: Ray 33 'in parallel light flux ... Regular reflected light F1 of ray 33 ... Focal length F2 of collimating lens ... Focal length F3 of object side lens ... Focus of image side lens Distance F4 ... Focal length F5 of the micro lens ... Focal length D1 of the shared lens .. Parallel beam diameter D2 before incidence on the object side lens D ... Parallel beam diameter D3 after emission from the image side lens D ... Parallel beam diameter D4 before incidence on the minute lens P ... Parallel beam diameter P after emission from the shared lens ..Point P2 where the focal point of the object side lens and the focal point of the image side lens coincide with each other. Point P3 where the focal point of the minute lens coincides with the focal point of the shared lens. The light beam emitted from the off-axis optical system is the optical axis. Intersecting point L: Length of cylindrical object
J: Deviation amount between the optical axis of the microlens and the optical axis of the shared lens in the off-axis optical system θi: incident angle θi0 of the principal ray of the parallel beam incident angle θi1 of the ray 30 in the xy section ..An incident angle .theta.i2 in the xy section of the light beam 31 .An incident angle .theta.i3 in the xy section of the light beam 32 .An incident angle .theta.c in the xy section of the light beam 33. The angle θa formed in the xy section of the optical axis of the focal optical system unit: the angle formed between the optical axis of the camera and the central axis of the cylindrical object

Claims (7)

A plurality of illumination means for emitting parallel light are arranged around an axis obtained by extending the cylindrical axis of the cylindrical object,
An illumination device that illuminates the cylindrical surface with light from the plurality of illumination means obliquely with respect to the normal line,
The plurality of illumination means includes:
The vertical distances from the cylindrical axis are equal, and the incident angles of the principal rays of the light when irradiating the cylindrical surface of the cylindrical object are equal to each other. Lighting device. Each of the plurality of illumination means is
The light source;
A collimating optical system that collimates the light emitted from the light source unit;
A first optical system for collecting light from the collimating optical system;
Having an optical axis on the optical axis of the first optical system;
The illumination apparatus according to claim 1, further comprising: a second optical system that emits the light collected by the first optical system as parallel light. Among the plurality of illumination means, one illumination means is
The light source;
A collimating optical system that collimates the light emitted from the light source unit;
A first optical system for collecting light from the collimating optical system;
2. The illumination apparatus according to claim 1, further comprising a shared optical system that shares the light collected by the first optical system with another illumination unit that emits the light as parallel light. A plurality of illumination means for emitting parallel light are arranged around an axis obtained by extending the cylindrical axis of the cylindrical object,
An illuminating device that illuminates the cylindrical surface with light from the plurality of illumination means obliquely with respect to the normal line;
An imaging device for photographing the cylindrical surface;
From the image information obtained by the imaging device, a surface state inspection device having processing means for inspecting the surface state on the cylindrical surface,
The plurality of illumination means includes:
The vertical distances from the cylindrical axis are equal, and the incident angles of the principal rays of the light when irradiating the cylindrical surface of the cylindrical object are equal to each other. Surface condition inspection device. Each of the plurality of illumination means is
The light source;
A collimating optical system that collimates the light emitted from the light source unit;
A first optical system for collecting light from the collimating optical system;
Having an optical axis on the optical axis of the first optical system;
5. The surface condition inspection apparatus according to claim 4, further comprising: a second optical system that emits the light condensed by the first optical system as parallel light. Among the plurality of illumination means, one illumination means is
The light source;
A collimating optical system that collimates the light emitted from the light source unit;
A first optical system for collecting light from the collimating optical system;
5. The surface condition inspection apparatus according to claim 4, further comprising a shared optical system that shares the light condensed by the first optical system with another illumination unit that emits the light as parallel light. Around an axis extending the cylindrical axis of a cylindrical object,
Illumination in which a plurality of illuminating means are arranged so that the vertical distances from the cylindrical axis are equal and the incident angles of the principal rays of light are equal to each other when illuminating parallel light onto the cylindrical surface of the cylindrical object An irradiation step of illuminating the cylindrical axis with light from the device obliquely with respect to the normal line;
A photographing step of photographing the cylindrical surface with an imaging device;
Processing the image information obtained by the imaging device with a processing means, and inspecting defects on the cylindrical surface;
A surface condition inspection method characterized by comprising: